Fundamentals of Liquid Measurement David Beitel Davis & Davis Company Rocky Mountain Measurement Association 2015 Trade Show
Fundamentals of Liquid Measurement
David Beitel
Davis & Davis Company
Rocky Mountain Measurement Association
2015 Trade Show
Fundamentals of Liquid Measurement
Wouldn't life be a lot easier if all liquidhydrocarbon transactions would occur withthe same product, at the sametemperature and pressure, with the samequality ?
Fundamentals of Liquid Measurement
If it were all that easy, we wouldn't be able to allget together every year at the Trade ShowSchool !
We have the School for a reason, so there mightbe something more to it …
Fundamentals of Liquid Measurement:Physical Properties
To minimize the overall measurement uncertaintyin liquid petroleum measurement, a fundamentalunderstanding of the physical properties thataffect measurement is necessary.
Fundamentals of Liquid Measurement:Physical Properties
Importance of the Physical Properties
The specific physical properties of the unique‘hydrocarbon liquid’ will determine: The type of equipment installed to determine ‘custody
transfer’ quality numbers,
The equations used to correct the product’s behavior tovarying operating conditions
The techniques used for calibration and maintenance.
Fundamentals of Liquid Measurement:Physical Properties
Some of the Physical Properties that we will discussthat will affect the design, and the operation ofthe measurement station include:
Composition,
Temperature,
Pressure,
Density,
Sediment and Water,
Vapor Pressure,
Viscosity.
What is a liquid ?
Supercritical Fluid Region
Liquid Region
2 Phase Region
Critical Point
Cricondenbar
Vapor
Regio
n
Cricondentherm
Fundamentals of Liquid Measurement:Composition
Cricondentherm:
The Cricondentherm is defined as themaximum temperature above which liquidcannot be formed regardless of pressure.
Fundamentals of Liquid Measurement:Composition
Cricondenbar
The Cricondenbar is the maximumpressure above which no gas can beformed regardless of temperature.
Fundamentals of Liquid Measurement:Composition
Composition
Not all ‘Liquid Hydrocarbons’ are the same.
Composition will determine ‘what we call theproduct ’.
Composition will determine how the product‘behaves’ at operating conditions.
Fundamentals of Liquid Measurement:Composition
Composition What really is the Liquid?
NGL - Condensate
Y-Grade
Natural Gasoline (c6 –c8)
LNG
Crude Oil
Heavy ?
Light ?
Pure Product
Propane?
Butane ?
Fundamentals of Liquid Measurement: Part 1Composition
All Hydrocarbon liquids are made up of Carbon andHydrogen.
Molecules can be separated into their individualcomponents without a chemical reaction.
The analysis of individual components can be determinedfrom Liquid Chromatography.
Name Carbon Hydrogen Formula
Methane 1 4 CH4
Ethane 2 6 C2H6
Propane 3 8 C3H8
Butane 4 10 C4H10
Pentane 5 12 C5H12
Hexane 6 14 C6H16
Heptane 7 16 C7H16
Octane 8 18 C8H18
Nonane 9 20 C9H20
Decane 10 22 C10H22
METHANE MOLCULE: CH4
ETHANE MOLUCULE: C2H6
PROPANE MOLCULE: C3H8
BUTANE MOLCULE:C4H10
PENTANE MOLCULE:C5H12
HEXANE MOLCULE:C6H16
HEPTANE MOLCULE : C7H13
OCTANE MOLCULE:C8H18
Fundamentals of Liquid Measurement Part 1:Solution Mixing
Solution Mixing
Natural gas liquid mixtures especially thosecontaining lighter ends will experience lowertotal volumes than the combined volume of theindividual components.
Fundamentals of Liquid Measurement Part 1:Solution Mixing
A Practical Example….
Fundamentals of Liquid Measurement:Composition
Composition Terms
Mole Percent Relates the number of Molecules for a particular
component to the total number of molecules in theliquid.
M.P. = Number for Molecules of component * 100
Total number of Molecules
Fundamentals of Liquid Measurement:Weight Percent
Weight Percent:
Mass of each component divided by the totalmass of the composition
W.P. = Mass of Component * 100
Mass of Composition
Fundamentals of Liquid Measurement:Volume Percent
Volume Percent
Volume of the individual component divided bythe total volume of the composition.
V.P. = Volume of Component * 100
Total Volume of Mixture
Typical Natural Gas Liquid Composition
Mole % Mole Weight Mass- LBM Weight Fraction Weight Percent
Methane 0.0 16.043 0.0 0.0 0.0
Ethane 0.2 30.07 0.0601 0.00078 0.07799
Propane 2.0 44.097 0.8819 0.0114 1.1437
Iso-Butane 7.5 58.123 4.3592 0.05653 5.6532
Normal-Butane 7.5 58.123 4.3592 0.05653 5.6532
Iso-Pentane 25.5 72.15 18.398 0.2386 23.8597
Normal-Pentane 25.5 72.15 18.398 0.2386 23.8579
n-Hexane 16.47 86.177 14.1933 0.18406 18.4066
Heptanes 7.5 100.204 7.5153 0.09746 9.746
Octanes + 7.83 114.231 8.9442 0.1159 11.5994
Totals 100 77.1099 1.00 100.0
Typical Crude Oil Composition
Methane 0.2390 0.0335 0.0835
Ethane 0.2938 0.0773 0.1625
Propane 1.0957 0.4227 0.6230
Isobutane 1.0421 0.5298 0.7034
n-Butane 1.6354 0.8315 1.0639
Neopentane 0.1743 0.1100 0.1378
Isopentane 2.1034 1.3275 1.5887
n-Pentane 1.9377 1.2229 1.4481
2,2-Dimethylbutane 0.1945 0.1466 0.1675
2,3-Dimethylbutane 0.5789 0.4364 0.4894
2-Methylpentane 1.7079 1.2875 1.4624
3-Methylpentane 1.0428 0.7861 0.8779
n-Hexane 2.5077 1.8904 2.1272
Heptanes 23.0747 19.4277 19.3564
Octanes 16.3885 15.0922 14.7522
Nonanes 21.7218 21.8364 20.4648
Decanes plus 24.2353 34.5348 34.4851
Nitrogen 0.0274 0.0067 0.0062
Carbon Dioxide 0.0000 0.0000 0.0000
Component Mole% Weight % Liquid Volume %
Total 100.0000 100.0000 100.0000
Fundamentals of Liquid Measurement:Fundamental Calculations
GPA Standard 8182-03, API MPMS 14.7 dictate themethods that determine proper Mass Methods ofLiquid Hydrocarbons. Generally Mass Measurement techniques are used for liquids
in the .350 < SG <.689 range.
Per the Standard:
Volumes derived from mass measured quantities arealways higher than the quantities measured on avolumetric basis for these streams.
Properties Standard: GPA 2145
Calculation example
Component COMPONENT std
Name INMOL % mw lb-mass weight weight density 1/f gal volume vol
fraction % lb/gal fraction %
n2 0
co2 0
c1 0 0 16.043 0 0 0 1.6 0.625 0 0 0
c2 0.2 0.002 30.07 0.06014 0.00072045 0.07204516 2.9714 0.3365417 0.02023962 0.0013211 0.13211008
c3 2.2 0.022 44.097 0.970134 0.01162179 1.16217919 4.2301 0.23640103 0.22934068 0.01496976 1.4969757
ic4 5.5 0.055 58.123 3.196765 0.03829588 3.82958822 4.6934 0.21306516 0.68111923 0.0444587 4.44587043
nc4 5.45 0.0545 58.123 3.1677035 0.03794774 3.79477379 4.8696 0.20535568 0.65050589 0.04246048 4.24604795
ic5 22.62 0.2262 72.15 16.32033 0.1955106 19.5510598 5.2074 0.19203441 3.13406498 0.20456986 20.4569864
nc5 25.5 0.255 72.15 18.39825 0.22040319 22.0403194 5.2618 0.19004903 3.49656961 0.22823163 22.8231633
c6 10.2 0.102 86.177 8.790054 0.1053011 10.5301101 5.5363 0.18062605 1.58771273 0.10363479 10.3634793
c7 8.5 0.085 100.204 8.51734 0.1020341 10.2034103 5.7375 0.17429194 1.4845037 0.09689803 9.68980292
c8 9.83 0.0983 114.231 11.2289073 0.13451752 13.4517524 5.8942 0.16965831 1.90507742 0.12435014 12.4350142
c9 10 0.1 128.258 12.8258 0.15364762 15.3647618 6.0183 0.16615988 2.13113338 0.1391055 13.9105496
Totals 100 83.4754238 15.3202672 1 100
Fundamentals of Liquid Measurement Part 1:Practical Application of Temperature
I would like to buy oil from you at a coldertemperature,
And I would like to sell oil to you at a warmertemperature.
Fundamentals of Liquid Measurement Part 1:Practical Application
WHY ?
Liquids contract with decreasing temperature.
I would actually get more oil – on a volumetricbasis.
Liquids expand with increasing temperature.
I would actually sell less oil – on a volumetricbasis
Fundamentals of Liquid Measurement Part 1:Temperature Compensation
Operating temperatures are never the same and vary fromminute to minute.
Fluids will expand with increasing temperature, and contractwith decreasing temperature.
Correction equations have been developed, as a function ofdensity to correct the fluid to a standard of 60 F.
CTL and CPL factors are actually factors that attempt tocorrect for the density change of the product.
The Temperature Correction Factor must be used: CTL.
Fundamentals of Liquid Measurement: Part 1Temperature
For liquids that maintain constantexpansion relationships with temperature,various equations have been developed,primarily based on gravity to correct to astandard temperature in the US of 60 F.
Temperature Effects: CTL Factors
TempDeg F
45.0 API 45.5 API 46.0 API 46.5 API 47.0 API
75.0 0.9920 0.9920 0.9919 0.9919 0.9918
75.5 0.9917 0.9917 0.9916 0.9916 0.9915
76.0 0.9915 0.9914 0.9913 0.9913 0.9913
Fundamentals of Liquid Measurement:Computer Equations
In modern Flow Computers it is much easier to calculate theCTL factor without the Tables, but with an equation. The APIalgorithms uses density, temperature, and thermal expansionfactor to determine CTL:
VCF = ρτ/ρ60 = EXP[-α 60∆τ(1+0.8α 60∆τ)]
In which:VCF = Volume Correction Factor
ρτ = density at temperature τ
ρ60 = density at 60˚F
α 60 = thermal coefficient of expansion for that type of liquid at 60˚F
∆τ = τ – 60.0
Fundamentals of Liquid Measurement:Pressure
Like temperature, operating pressures are neverthe same and vary from minute to minute.
Hydrocarbon liquids are compressible, and willcontract when pressure is increased, and expandwhen pressure is decreased.
Liquid Volumes corrected to 14.696 or theirequilibrium vapor pressure.
Fundamentals of Liquid Measurement:Pressure
The net effect of the expansion and contractionof the liquid is the associated density change
CPL factors are actually factors that attempt tocorrect for the density change of the product dueto the application of pressure different than thestandard pressure.
Pressure Effects: CPL Correction
CPL = 1/[1(P – Pe) * F]
In Which:
P = Operation pressure in PSIG
Pe = Equilibrium vapor pressure at operatingpressure ( or zero for liquids with vapor pressuresless than atmospheric)
F = Compressibility factor
Pressure Effects:
Compressibility Factors at 500psi
Temp Deg F 18.0 18.5 19.0 19.5 20.0
99.0 0.00000434 0.00000437 0.00000440 0.00000444 0.00000447
99.5 0.00000434 0.00000437 0.00000441 0.0000444 0.00000448
100.0 0.00000435 0.00000438 0.00000441 0.00000444 0.00000448
CPL Factor at 500 psi
18.0 18.5 19.0 19.5 20
99.0 1.00217 1.00219 1.00200 1.00225 1.00224
99.5 1.00217 1.00219 1.00221 1.00225 1.00245
100.0 1.00218 1.00219 1.00221 1.00225 1.00245
CPL Example
Crude Oil with a 20.0 API Gravity (at 60.0 F)metered at a pressure of 500 psi and atemperature of 100F, has an ‘F’ factor of0.00000448 from Table 5. The corresponding CPLis:
CPL = 1 / [ 1- (500-0) * 0.00000448] = 1.0023
Does Pressure Really Matter?
Crude oil sensitivity to pressure
Fundamentals of Liquid Measurement:Density
Density is the term that will relate the volume ofthe fluid to the mass of the fluid.
Specific gravity: Ratio of Mass of a given volume of a substance to that of
an equal volume of another substance used as areference.
Relative Density Ratio of the density of a liquid at a given temperature to
the density of pure water at a standard temperature.
Fundamentals of Liquid Measurement:API Gravity
The American Petroleum Institute gravity, or API gravity, is ameasure of how heavy or light a petroleum liquid is comparedto water. If its API gravity is greater than 10, it is lighter andfloats on water; if less than 10, it is heavier and sinks.
Fundamentals of Liquid Measurement:API Gravity
Special Scale of relative densities used forHydrocarbon Liquids.
Degree API @ 60 deg F = 141.5 - 131.5
Relative Density
Fundamentals of Liquid Measurement: API Gravity
Petroleum Liquid Relative Densities API Gravity Range
Crude Oil 1.00 – 0.78 10 - 50
Fuel Oils, Jet Fuel 0.875 – 0.780 30 - 50
Gasoline 0.780 – 0.685 50 - 75
Natural Gas Liquids 0.50 – 0.68 75 - 110
Butanes - Propane 0.695 – 0.505 75 - 115
Fundamentals of Liquid Measurement:S&W
Not all hydrocarbon liquids are pure fluidsat the sales point.
Typical in Crude Oil custody transferswhere there is minimal processing,Sediment and Water must be accountedfor.
‘non-commercial volumes’
Fundamentals of Liquid Measurement:S&W
S & W is taken account of in two fashions
Continuous measurement to divert fluid into abypass tank if value is above specification.
Sampling of Hydrocarbon Liquid to determinethe CSW – Correction of Sediment and water.
Fundamentals of Liquid Measurement:S&W
Fundamentals of Liquid Measurement:Vapor Pressure.
The pressure at which liquid hydrocarbon is inequilibrium between it liquid and vapor state.
For a liquid at a given temperature, it refers tothe pressure at which bubbles just start to form.
‘Bubble Point Liquid’
Supercritical Fluid Region
Liquid Region
2 Phase Region
Critical Point
Cricondenbar
Vapor
Regio
n
Cricondentherm
Fundamentals of Liquid Measurement:Vapor Pressure.
Reid Vapor Pressure
Testing done at 100 deg F per ASTM D323-28
Usually the minimum specification for transportof Hydrocarbon Liquids is 10 RVP. Recently RVP Values of as low as 6 are being required.
Insures that losses due to evaporation, andflashing in meters is kept to a minimum.
RVP at 100 deg F in PSIA
Ethane 800
Propane 188.696
i-Butane 72.484
n-Butane 51.683
i-Pentane 20.456
n-Pentane 15.558
n-Hexane 4.961
n-Heptane 1.62
n-Octane 0.366
n-Nonane 0.17
n-Decane 0.616
Measurement of Liquids
Effect of Varying Composition: S.G.= 0.475
C1 C2 C3 C4 NC4 IC5 IC5 C6+ CO2 VP1.1 37.6 33.9 4.1 12.5 0.9 3.1 4.37 .37 492.71 39.4 31.0 4.8 11.9 3.4 3.4 5.21 .2 470.9 39.9 30.3 4.7 11.1 3.3 3.3 5.9 .42 4871.9 37.2 33.8 3.9 12.2 2.9 3.2 4.5 .45 546.65 39.3 31.6 4.7 12.1 3.3 3.4 4.9 .13 464.96 37.2 34.3 5.2 12.9 3.1 2.8 3.5 0 4761.4 36.7 33.5 5.2 12.9 3.3 3.1 3.8 0 510.86 40.7 29.4 4.5 10.9 3.4 3.2 6.7 .29 490.87 36.9 34.9 5.5 12.9 3.2 2.8 2.9 0 466.46 41.7 28.7 4.5 10.5 3.4 3.4 6.8 .45 464
Fundamentals of Liquid Measurement:Viscosity
Viscosity is the characteristic of a fluid thatcauses it to resist flow.
The higher value of Viscosity the greater it’sresistance to flow.
Fundamentals of Liquid Measurement:Viscosity
Fundamental unit of absolute viscosity is the Poise.
Kinematic Viscosity is absolute viscosity divided bydensity represented in units of Centistokes: cSt.
Including density is more useful in predictingpressure loses in meters, pumps, and pipe frictionloss.
Temperature Dependency
Types of Viscous Fluids
Viscosity of Crude Oil
Viscosity of Ketchup
Fundamentals of Liquid Measurement: Part 1
Questions ?
Fundamentals of Liquid Measurement:Degree Baume
The U.S. National Bureau of Standards in 1916 established theBaumé scale (see: Degree Baumé) as the standard formeasuring specific gravity of liquids less dense than water (see:Density of water). Investigation by the U.S. National Academyof Sciences found major errors in salinity and temperaturecontrols that had caused serious variations in published values.Hydrometers in the U.S. had been manufactured and distributedwidely with a modulus of 141.5 instead of the Baumé scalemodulus of 140. The scale was so firmly established that by1921 the remedy implemented by the American PetroleumInstitute was to create the API Gravity scale, recognizing thescale that was actually being used.